The illustrated diary, one of 500 lots, has an estimate of €50,000 ($56,860) and covers the period of time when Dalí seduced Gala, who was living at the time in a “relationship-a-trois” with her husband Paul Éluard and Max Ernst. She left them to marry Dalí, with whom she remained despite many rumored affairs.

Diary belonging to Salvador Dali Photo: courtesy of Sotheby’s Paris

The private collection, built up by a father and son, is thought to be one of the best collections of Surrealist art and artifacts in existence and is estimated to reach a grand total of around €4 million ($4,550,053).

Diary belonging to Salvador Dali Photo: courtesy of Sotheby’s Paris

Other items in the sale include 21 portraits of Gala by Éluard, illustrated letters, photographs, and poetry by André Breton, René Magritte, Joan Miró, Max Ernst, and Roland Penrose, and others involved in the movement.

There are also works and ephemera by Pablo Picasso up for sale: these include around twenty sketches and drawings, letters, postcards, and even a doodle on a menu.

A drawing by Picasso, sent on a postcard Photo: courtesy Sotheby’s Paris

There is one particular postcard from the deeply intimate collection sent from Picasso to Éluard, signed by a group on holiday including Picasso’s lover Dora Maar, inscribed with “Ici on aime ses amis” or “Here we love our friends.” It is rare to have such a genuine insight into the lives of artists involved in both a much-loved movement such as Surrealism and in deeply personal, lifelong relationships, as the Guardian points out.